This invention relates to a sensor system for automatically aligning television-picture-tube deflection systems to achieve horizontal and vertical pincushion correction.
A sensor system of this kind is disclosed in Offenlegungsschrift DE 28 05 691 Al, which corresponds to U.S. Pat. No. 4,277,797. It coacts with an alignment computer, a pattern generator, a memory, and a digital deflection control unit to compensate for the geometric distortion due to the screen curvature in such a way that the reproduced image is free from those distortions. The system thus performs both horizontal (east-west) and vertical (north-south) pincushion correction. The sensor system in the prior art arrangement consists, for example, of a photodiode moved by a motor on a rail at a predetermined speed along, e.g., the left side of the picture from the top to the bottom, cf. page 32 of DE 28 05 691 Al. As an alternative, a strip fitted with 156 photodiodes may be used which need not be driven by a motor but is fixed, cf. page 32 of that Offenlegungsschrift. This known sensor system is quite costly and complicated since it requires either a motor drive or a large number of photodiodes.